This invention relates in general to gas detector systems and more particularly, to an enclosure for such a system, including a battery/gas sensing cell or battery/sensor holder and holder absence indicator.
Airborne gases and vapor, some of which are toxic and others of which are flammable or otherwise dangerous, such as propane, methane, carbon monoxide, mercury, ethylene oxide, volatile organic compounds, hydrogen sulphide, etc. are difficult to detect, especially where they are odorless or present at levels that cannot be smelled or masked by other odors. The danger of these is becoming increasingly apparent, especially in industrial plants, mines, well-sealed homes and office buildings, recreational and other vehicles and other environments in which people are present for long periods.
Recently, a solid state biomimetric sensor has been developed by the inventor of the present application which has an extended useful life and which mimics the human response to various toxic gases and vapors. As described in U.S. Pat. No. 5,063,164 this sensor comprises a porous, semi-transparent substrate with a self-regenerating chemical sensing reagent impregnated into the substrate. The Optical density of the chemical sensor changes in response to contact with the target gases. This patent describes a variety of sensing reagents and substrates.
The sensor has a relatively long useful lifetime, typically about three years, approximately equivalent to the useful life of typical alkaline battery. A gas detector system is also described in co-pending U.S. Pat. No. 5,280,273 issued to the present inventor on Jan. 18, 1994.
Other gas sensing compositions have been developed, such as those described by Shuler et al in U.S. Pat. No. 4,043,934. The disclosed sensing reagents are effective with certain gases, such as reducing gases like carbon monoxide, producing a color change upon exposure. These materials however, tend to have a short useful life, typically 2-4 months.
In order to apply these gas sensing materials in practical applications, such as commercial, industrial, home, recreational vehicle or other uses, compact, reliable, easily serviced sensing and alarm systems are needed. The system must provide accurate and reliable detection of optical transmission characteristics and/or color changes. Characteristics of certain sensor materials, such as variable response depending on ambient humidity, must be accommodated. Ease of servicing, e.g., replacement of the sensing material or cell and battery, battery pack or main power supply, is an important consideration where unskilled persons are maintaining the system.
In most cases, the gas detectors are most effective when fastened to the ceiling in an area where there is free air flow. The detector enclosure should be attractive, be convenient to service. Battery changing, sensor or sensing cell replacement and the like should be simple to accomplish without requiring special tools, ladders, etc. Thus, there is a continuing need for improved enclosures for single and multiple gas detectors that allow highly efficient detector operation, are easily serviced, clearly indicate the presence of toxic gases, clearly show when the battery or other power supply is missing and are attractively configured.